Corrosion inhibiting compositions



Patented Nov. 18, 1941 George F. Rouault, Whiting, Ind., assignor toStandard Oil Company, Chicago, Ill.,. a corporation of Indiana No-Drawing. Application November 27, 1943,

Serial No. 512,047

'12 Claims.

1 This invention relates to corrosion inhibiting compositions forprotecting metal surfaces, particularly those of ferrous andrelatedmetal or alloy products, from the corrosive action of air or oxygen inthe presence of moisture or other aqueous liquids. More particularly,the present invention relates to corrosion inhibiting oil compositionsadapted for use in systems which employ water or steam or which maybecome contaminated with water, steam or other aqueous liquids whichnormally cause corrosion and/or rusting of metal surfaces.

In various machines and industrial equipment in which water or steam orother aqueous liquids are used or which may become contaminated withsuch aqueous media. rusting or corrosion of the metal parts,particularly ferrous metal parts, is encountered, causing materialdamage to such equipment. For example, in internal combustion engineswater due to condensation accumulates in the crankcase and frequentlycauses rusting and/or corrosion of the ferrous metal parts of suchengines. In the operation of steam turbines rusting or corrosion of theferrous metal parts of such systems is also a serious problem, and theprevention or inhibition of such rusting. or corrosion is highlyimportant. Corrosion due to the presence of aqueous medium is also aserious problem in the operation of textile machinery, in shockabsorbers, in hydraulic lifts and the like. Although equipment of theforegoing type usually employs an oil of some sort, the oil film whichmay form on the ferrousmetal surfaces does not provide adequateprotection against rusting and/or corrosion by aqueous liquids, due tothe partial displacement of this oil film from the metal surfaces bysteam, water or other corrosive aqueous media.

It is an object of the present invention to provide an oil compositionwhich will effectively inhibit or prevent the rusting or corrosion ofmetal parts of equipment which come in contact with water, steam orother corrosive aqueous liquids.

It is another object of the present invention to provide an oilcomposition which will inhibit corrosion of metal surfaces wherever themetal comes in contact with fluids causing or tending to cause corrosionof the metal surfaces.

Still another object of the invention is to provide an oil compositionwhich will afford adequate protection against corrosion and/or rustingto metal surfaces exposed to the effects of moisture and oxygen jointlyand normally tending to corrode and/or rust.

Another object of the invention is to provide an oil composition whichwill inhibit corrosion to ferrous metal surfaces by humid atmospheres.

Another object of the invention is to provide a method by which normallycorrosive liquid mixtures having a corrosive constituent and anoncorrosive constituent may be treated to render the mixture as a wholenon-corrosive.

A further object of the invention is to provide a method of preventingrusting and/or corrosion to metal parts of equipment in which water orsteam is used or which may become contaminated with water, steam orother corrosive aqueous media.

Still another object of the invention is to provide a steam turbinelubn'cant which effectively inhibits or prevents the orrosion and/orrusting of metal surfaces of such steam turbine systems which come incontact with water or steam.

Other objects and advantages of the invention will become apparent fromthe following description thereof.

I have discovered that the foregoing objects can be attained by addingto an oil, preferably a mineral oil having a viscosity within the rangesuitable for steam turbine lubrication, small amounts; namely, fromabout 0.005% to about 0.1% of an alkylammonium naphthenate andpreferably the primary and secondary alkylamine Although thealkylammonium naphthenates of the foregoing type all have to a definitedegree corrosion and/or rust-inhibiting properties, all of them are notnecessarily equivalent in their effectiveness. They may exhibit somevariation depending on the nature and severity of the service in whichthey are employed, the nature of the metal to be protected, etc.

Alkylammonium naphthenates of the type above described can be readilyprepared by warming and stirring a. mixture of naphthenic acid with anequivalent amount of the desired amine 3 mtil the mixture becomeshomogeneous. The iikylammonium naphthenate may, if desired, be formed insitu in the oil by the simple procedure Jf adding the desired alkylamine, for example amylamine, and the naphthenic acid to the oil orother oleaginous material.

Naphthenic acids are complex mixtures of carboxylic acids which occurnaturally in various crude petroleum oils, usually in proportions below1 per cent, and which may be extracted therefrom by the use of alkalies.has demonstrated that petroleum naphthenic acids fall into at leastthree general categories: (1) aliphatic acids having the general formulaCnHznOz and predominating in compounds wherein n is 6 to 7, (2) acidshaving the general formula cnHzn-aOz and shown to be cyclopentanederivatives CsH9.(CI-I2):CO2H, where a: generally varies from 1 to about4 and wherein the cyclopentane ring may also contain one or more alkylgroups, (3) acids having the general formula CnH2fl402, known to containa bicyclic ycloaliphatic nucleus and containing about 12 to about 25carbon atoms. The above classification presents a somewhatover-simplified picture Some evidence has been adduced of the existenceof even more complex acids in petroleum naphthenic acids, includingtriand tetra-cyclic cycloaliphatic-substituted aliphatic carboxylicacids. There is evidence that the molecular weights in the above classesoverlap; thus, although the simple aliphatic acids predominate in Co orC1, small proportions of higher molecular weight fatty acids also occurand overlap into the molecular weights and boiling ranges of compoundsfalling into categories (2) and (3) above. Naphthenic acids obtainedfrom different crudes and from various fractions of the same crude oilgenerally differ from each other somewhat in composition and character.For the purposes of the present invention the naphthenic acids obtainedfrom petroleum or other sources can be suitably employed.

Although the alkylammonium naphthenatesof the class'described, when usedin small amounts in hydrocarbon oils, are effective corrosion and/orrust inhibitors, when employed in systems which contain moisture orwater or which may become contaminated by moisture or water, a preferredapplication of these alkylammonium naphthenates as corrosion and/or rustinhibitors is in the viscous, highly refined hydrocarbon oils, such assteam turbine oils which generally have Saybolt viscosities at 100 F. offrom about 125 seconds to about 2000 seconds and higher. The drasticrefining treatments required to produce more highly refined turbine oilshaving improved sludge resistance and emulsification properties removesthe desirable components of oils responsible for the rust inhibitingqualities of the oil. The oils thus produced are inferior with respectto rust inhibiting qualities to moderately refined oils, which givefairly good protection against rusting. The steam turbine rusting isusually encountered in the upper portion of the oil reservoirs and otherparts of the system, being caused by droplets of water coming in contactwith the steel surfaces which have been covered by the oil anddisplacing a part or a portion of the oil. It is thought that mostanti-rust additives suitable for use in turbine oil protect ferrousparts by plating out thereon and forming a, thin film impervious towater. In the presence of oils which provide inadequate protection, theferrous surfaces are, attacked by the water with formation of ferricoxide Extensive research 4 and black magnetic oxide. As the rustingprogresses these oxides scale off and may be carried in suspension inthe oil, often scoring bearings, plugging oil lines and causing faultyoperation or sticking of the delicate governor parts. The need fornon-rusting turbine oils is therefore great.

The anti-rust activity of turbine oils containing the salt of analiphatic amine and an Organic acid is demonstrated by the followingtest: 300 cubic centimeters of the oil to be tested are placed in a, 400cc. glass beaker and heated to about 163 F. in an oil bath and the oilagitated with a stirrer maintained at about 7 50 R. P. M. When thetemperature of the oil sample reaches about 163 F., a cleaned test stripof cold rolled steel is suspended in the oil and stirring continued for30 minutes to insure complete wetting of the steel specimen. Thirtycubic centimeters of distilled water are then carefully added by'pouringit down the side of the beaker; stirring is continued for 48 hours. Atthe end of this period the specimen is removed from the beaker, washedwith naphtha and visually inspected forthe presence of rust. This testis a modification of the American Society for Testing Materials Proposedtentative method of test for rust-preventing characteristics ofsteam-turbine oil in the presence of water,

D665-42T. The method of carrying out this test is fully described inNational Petroleum News,

section 2, volume 3 number 30, July 29, 1942,v

page R-216.

The effectiveness of the salts of aliphatic amines and organic acids ascorrosion' inhibitors, as determined by the foregoing test, isdemonstrated by the following results:

1 Prepared from naphthenic acid and the mixed monosmylaminescommercially available.

2 Prepared from naphthenic acid and the mixed diamylamines commerciallyavailable.

In systems in which oil comes in contact with water, it is essentialthat any emulsification which may occur be of a quick breaking type. Itis therefore important that any additive which may be used in such oilsbe of a type which will not cause stable emulsions to be formed. One ofthe advantages of employing the alkylammonium naphthenates for theherein described purpose is that they have substantially no tendency tocause stable emulsification. One of the standard methods of determiningthe emulsification tendency of oils under service conditions is theso-called Herschel Demulsification test, described in the Bureau ofStandards Technological Paper No. 86 (1917). A petroleum oil used as acontrol, when subjected to the Herschel Demulsification test, gave aHerschel Demulsification number at F. of 1620. The same oil containing0.2% of amylammonium naphthenate gave substantially the same result;namely, a Herschel Demulsification number at 130 F. of 1500, thusdemonstrating the non-emulsifying properties of such soaps.

To inhibit the oxidative deterioration of the oils susceptible to suchdeterioration small amounts of known antioxidants can be added to theoils in combination with the alkylammonium naphthenates. Antioxidantssuch as the Polyhydric phenols and their alkyl derivatives, for example,catechol, tertiary-butyloatechol and octylcatechol, can be used. Otherefiective antioxidants are cresol, pyrogallol, hydroquinol, and otherhydroxy condensed ring compounds and their alkyl derivatives, such asbeta-naphthol, octyl beta-naphthol, amyl beta-naphthol, laurylbeta-naphthol, alpha-naphthol, cetyl alphanaphthol, amyl alpha-naphtholand other alkyl derivatives of betaand alpha-naphthols. Otherantioxidants such as phenyl alpha-na'phthylamine, diphenylamine, butylpara-aminophenol, etc, can be used. The amount of antioxidant employedwill depend uponthe effectiveness of the particular material used, butin general will range in quantity from about 0.001% to about 0.25%.Thus, I have found that a suitable turbine oil having a SayboltUniversal viscosity at 100 F. of from about 150 seconds to about 330seconds exhibiting non-rusting properties and resistant to oxidativedeterioration is one containing from about .005% to about .1%alkylammonium naphthenate and from about 0.02% to about 0.2% ofN-phenyl-alpha-naphthylamine.

A turbine oil composition which gave extremely satisfactory results isone comprising a highly refined mineral oil having a Saybolt Universalviscosity at 100 F. of about 160 seconds, 0.1%phenyl-alpha-naphthylamine and 0.05% amylammonium naphthenate. Thisturbine oil when subjected to the Proposed method of test for oxidationcharacteristics of steam-turbine oils, directions for which have beenpublished on pp. 17-20 of A. S. T. M. Standards on Petroleum Products.Committee D 2, 1943, has lasted over 3300 hours. This stability isstriking when compared with the life of a commercial turbine oil ofabout 800 to 900 hours. This turbine oil containing thephenyl-alpha-naphthylamine and. the amylammonium naphthenate permittedonly very slight rusting of the iron in the oil layer even after 3300hours under the very drastic conditions of the A. S. T. M. turbine oiloxidation test, which is carried out at 203 F. in the presence of 20%water and copper and under conditions in which oil is saturated withoxygen and continuously agitated.

In addition to the alkylammonium naphthenates, the non-corrosivecomposition may, if desired, contain other adjuncts such as fatty acids,for example stearic acid, extreme pressure lubricants, sludgeinhibitors, V. I. improvers, etc.

The alkylammonium naphthenates can also be used as corrosion and/or rustinhibitors in vegetable, animal, and marine oils, or in blends of suchoils with hydrocarbon oils.

While I have illustrated the present invention by various specificexamples thereof, it is not intended to limit the scope thereby exceptin so far as the same is defined by the following claims.

I claim:

1. A turbine oil consisting essentially of a highly refined hydrocarbonoil, from about 0.005% to about 0.1% of an alkyl amine soap ofnaphthenic acid, selected from the group consisting of primary alkylamine soaps of naphthenic acids, and secondary alkyl soaps of naphthenicacids, in which each alkyl; radical contains from about 4 carbon atomsto about 16 carbon atoms. and from about 0.001% to about 0.25% of ananti-oxidant selected from the group consisting ofphenylalpha-naphthylamine, diphenylamine', and butyl para-amino-phenol.

2. A turbine oil consisting essentially of a highly refined hydrocarbonoil, from about 0.005% to about 0.1% of a primary alkyl amine soap ofnaphthenic acid in which the alkyl radical contains from about 4 carbonatoms to about 16 carbon atoms and from about 0.001% to about 0.25% ofphenylalpha-naphthylamine.

3. A turbine oil as described in claim 2 in which the primary alkylamine soap of naphthenic acid is mono-amylammonium naphthenate.

4. A turbine oil consisting essentially of a highly refined hydrocarbonoil, from about 0.005% to about 0.1% of a secondary alkyl amine soap ofnaphthenic acid in which each alkyl radical contains from about 4 carbonatoms to about 16 carbon atoms and from about 0.001% to about 0.25% ofphenylalpha-naphthylamine.

5. A turbine oil as described in claim 4 in which the secondary alkylamine soap of naphthenic acid is di-amylammonium naphthenate.

6. A turbine oil as described in claim 4 in which the secondary alkylamine soap of naphthenic acid is di-dodecylammonium naphthenate.

7. A turbine oil consisting essentially of a highly refined hydrocarbonoil and from about 0.005% to about 0.1% of an alkyl amine soap ofnaphthenic acid selected from the group consisting of primary alkylamine soaps of naphthenic acids and secondary alkyl amine soaps ofnaphthenic acids in which the alkyl radical contains from about 4 toabout 16 carbon atoms.

8. A turbine oil consisting essentially of a highly refined hydrocarbonoil and from about 0.005% to about 0.1% of a primary alkyl amine soap ofnaphthenic acid in which the alkyl radical contains from about 4 toabout 16 carbon atoms.

9. A turbine oil as described in claim 8 in which the primary alkylamine soap of naphthenic acid is monoamylammonium naphthenate.

10. A turbine oil consisting essentially of a highly refined hydrocarbonoil and from about 0.005% to about 0.1% of a secondary alkyl amine soapof naphthenic acid in which each alkyl radical contains from about 4 toabout 16 carbon atoms.

11. A turbine oil as described in claim 10 in which the secondary alkylamine soap of naphthenic acid is di-amylammonium naphthenate.

12. A turbine oil as described in claim 10 in which the secondary alkylamine soap of naphthenic acid is di-dodecylammonium naphthenate.

GEORGE F. ROUAULT.

REFERENCES CITED The following references are of record inthe file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,366,013 Duncan Dec. 26, 19442,382,699 Duncan Aug. 14, 1945 2,162,454 Guthmann June 13, 19392,275,264 Musselman Mar. 3, 1942 2,332,825 Zimmer Oct. 26, 10432,221,162 Ashburn Nov. 12, 1940 2,305,560 Schiermeier Dec. 15, 1942

